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ISDN Connection Management
Orbitor 3000 Reference Manual— 2-5
Protocol Awareness
For Connection Management to be effective, each of the Orbitors must be aware of the protocols used
within the data being transferred over the ISDN calls between them.
IP and IPX Client-Server sessions are established between devices located on the LANs that are routed by
the Orbitor Bridge/Router. If the Orbitor is to manage the ISDN calls between the routed LANs, the Orbitors
on each WAN end of the Client-Server session must be aware of the session and also must become actively
involved in the maintenance of the session. When an ISDN call is suspended, both the Client and the Server
must still believe that the session exists.
Suspension Process
The Orbitor maintains a table for each ISDN call made to a partner ISDN Orbitor in order to determine
when the ISDN call should be suspended during Connection Management.
Any number of LAN sessions may be currently using the established ISDN call to transfer data between the
client and the server. The Orbitor monitors the ISDN call for interesting traffic passed on each of the
sessions currently using the ISDN call. If no interesting traffic is observed on the ISDN call for a period of
time greater than the defined Idle Timer value, the ISDN call is suspended and disconnected. While the
ISDN call is suspended, the Orbitor will monitor the LAN sessions for interesting traffic and re-establish the
ISDN call when required.
A suspended ISDN call may only be re-established by the Orbitor initiating the suspension or by the partner
Orbitor that was connected just prior to the call being suspended. This prevents other Orbitors from tying up
the ISDN calls and interfering with the suspended calls.
ISDN calls may be connected and disconnected between the two Orbitors when required according to the
suspension and re-activation of the ISDN calls. When all of the sessions using the call in the table have been
closed, the call will be terminated and the ISDN B-channel becomes available for use to connect to a
different ISDN Orbitor. When the connection to the partner ISDN Orbitor is configured to use Auto-Call,
the ISDN call will be suspended when there are no sessions in the table.
Interesting Traffic
Interesting Traffic is defined as normal interactive user data for a session. Certain data exchanged during a
normal session is not considered to be interesting and usually is composed of keepalive messages, watchdog
messages, and routing messages. Non-interesting data is handled differently when Connection Management
is enabled.